Relay mechanism for vehicle brakes



Aug. 2 1927. 1,637,349

F. G. PARNELL RELAY MECHANISM FOR VEHICLE BRAKES Filed Oct. 21, 1926 Franna e f 2175/4 Patented Aug. 2, 1927.

UNITED STATES 1,637,349 PATENT OFFICE.-

rmmx cannon rammLL, or COVENTRY, ENGLAND, assreivoa or ONE-HALE T0TRIUMPH CYCLE comrm LIMITED, or covnnray, ENGLAND, A BRITISH com PANY.

Application filed October 21, 1926, Serial No.

This invention relates to relay mechanism for vehicle brakes, of thekind which comprises a cylinder and a piston therein actuated from afluid circulatory system whose pressure is built up by obstructing theflow in accordance with variations in the braking force as applied inthe usual manner through the brake pedal or the hand lever and alsotransmitted thereby to a valve controlling the circulatory system.

A construction has previously been proposed in which the fluid wascontrolled by a valve mounted within the piston and having a hollow stemextending through the end of the cylinder and connected to the pump by aconduit. The fluid entered the cylinder through a hollow piston rod andmade its exit through the hollow valve stem.

The principal object of the invention is to provide an improved methodof mounting and actuating the valve, and thus controlling the relayeffect whilst ensuring that the reaction upon the brake applying devicein creases with the magnitude of the relay effect obtained.

In the accompanyin drawings, which show a preferred metho of carryingout the invention,

Figure 1 is a sectional elevation taken on the axial line of the relaycylinder, and

Figure 2 is a plan view.

The relay cylinder 2 is located within a compartment 3 forming a lateralextension of a casing 4 containing the change speed transmissionmechanism of the vehicle.

a In this example the brakes are operated hydraulically and the relaypiston 5 is directly connected by a piston rod 6 with a smaller piston 7operating in a cylinder 8 coaxial with the cylinder 2 and constitutingpart of the hydraulic system, details of which form no part of thepresent invention.

The relay piston 5 has a tubular extension 9 extending slidably throughthe end wall 10 of the cylinder 2, the nature of the sliding fit beingsuch as to provide freedom of movement without undue leakage of pressure fluid from the cylinder. Around the tubular extension 9 and closeto its junction with the piston 5 are provided one or more ports 11through which the working fluid can flow from the cylinder into theextension.

At the 0 on end of .the tubular extension 9 is provide a disc or wingvalve 12 which RELAY MECHANISM FOR VEHICLE BRAKES.

143,214, and in Great Britain April 12, 1926.

seats at 13 around the end of the extension, and this valve is acted onby the toe 14 of a lever 15 mounted fast on a spindle 16 directly orindirectly connected with the brake lever or pedal (not shown) so that,when a braking pressure is applied, the eflect'is to thrust the valve onits seating 13. I

The end of the cylinder 2, together with the tubular extension 9, valve12, and the lever 15 which actuates the latter, are submerged in the oilor other fluid employed in the relay motor, the fluid level beingindicated by the chain line 17. The circulatory pump (not shown) ispositively driven by the shaft 18 at therear end of the gear box, thisshaft being in permanent connection with the rear driving wheels of thevehicle so that it is always in operation when the ve hiclc is inmotion. The pump may be contained in a separately formed casing which 18bolted on to the end of the gear box and its delivery port registerswith the relay cylinder inlet port 19, whilst its suction port registerswith the lower port 20 communieating, by the downward passage 21, withthe lower part of the compartment 3 containing the operating fluid,which in this case is the lubricating oil ordinarily supplied to thechange speed gear box. For this purpose, therefore, there is a passage22 connecting the compartment 3 with the interior of the gear box 4 andprovided with a filtering screen across it. The arrangement, therefore,is such that when the gear box is charged with lubricant a portionenters the compartment 3 containing the relay cylinder,

and the latter is properly submerged as above described, or conversely,the oil can be supplied into the compartment for the cylinder andthereby the supply to the gear box is ensured also.

0 In the operation of the relay device, it will be apparent that as longas the valve 12 at the end of the extension 9 remains open, the oildischarged from the circulating pump will, as shown by the arrows, flowthrough the end wall of the cylinder into the clearance space betweenthe piston and the end of the cylinder 2, thence through the pistonextension 9, and past the valve 12 into the lower part of thecompartment 3 from which the pump draws its supply. When pressure isapplied to the brake lever or pedal, the valve 12 is thrust towards itsseat, and the pressure in the. cylinder rises correspond- Ill -velopwear and lost motion.

areas of the valve 12 and of the piston 5will determine the ratio ofreaction pressure exerted upon the brake pedal or the like, and

this will be at all times proportional to the relayeifect obtained.

In the event of any failure of the relay mechanism, the brakes can stillbe actuated bythe usualflever or pedal, and it will be seen that as. theeffort of either is applied through the valve 12 direct to thepiston 5,the whole mechanismis very simple and avoids intermediate joints whichcould de- Also one set of transmission mechanism between the piston andthebrakes suflices both for the relay and for the usual applying member,whether pedal or lever;

In the, example above described, the flow of the circulatory fluid isunidirectional, and. as a consequence will reverse when the direction ofthe vehicle is reversed, but this is immaterial as the brakes can stillbe used in the ordinary manner. During such reverse movement, however,suctlon would take place through the port 19and delivery through theport 20, and to provide for this there is a nonreturn valve 23 whichconnects the suction and delivery sideand opens to allow a'free reversedcirculation. This valve may be mounted in a tubular casing 24.ext-endingfrom a removable'plng 25. which serves as a drain for thelower part of' the i compartment 3. The tubular casing is perforated atits lowerpartas shown at 26. to allow the fluid to reach the valve. v

To give ready access to the interior of the V compartment 3. forassembly or-examination of the parts of. the relay motor, it is providedwith a detachable cover27 with which the hydraulic cylinder 8 isintegrally formed, and a register 28 is provided on the Cover, therebyensuring accurate alignment of the cylinders 8 and 2. j j

The foregoing arrangement provides a simple and: accessible method ofmounting the-valve,- and it avoids the use of any flexible connections.and movin joints for-the connectiop of the suction am discharge conduitsrespectively communicating with the relayc linden.

Furt ierniore, the mounting of the control valve upon the piston of therelay motor yer y considerably simplifies the operative connectionbetween the brake lever or pedal "and the valve, and alsowit provides.for a very direct application of the braking force should the relayeffect failv through any cause. In this connection ;it is important toobserve that although a preferred arirangement is to ,employ the relaypiston to transmit. its efi'ort hydraulically to the brakes, yetgthey mit equally, well be .mechanically operated y'the use of an appropriatelink mechanism actuatedby the relay piston. The arrangement illustratedis, however, very simple and compact, having but few parts. Risk ofinsulii'cientoil forcirculation purposes is avoided through thecombination of the reserve supply contained in the compartnicntfi withthe contents of the changespced gear box. I

What I claim as my invention and desire to secure by Letters Patentol'the United States is 1.. In brake relay mechanism, thccombination of acylinder 'tliroughfwhich fluid is adapted to be circulated, apistontherein operatively connected with the brake and having a. portionprojecting outside the working party of said cylinder, an inlet port forsaidfiuid in the wall of said cylinder an exit port for said fluid inthat part of sai piston which projects outside said cylinder, a valvecontrolling said exit port, ant means for regulating exit therefrom ofsaid fluid by movcmentof said valve, substantially as set forth.

2. In brake relay mechanism, the combinationof a cylinder through whichfluid is adapted to be circulated, a piston thereinopcrativelyconnectedlwith the brake, a tubw lar extension of said"piston projecting beyond said cylinder end, an inlet port for saidfluid in the 'walloi said cylinder, a passage connecting the interior ofsaid cylinder with the interior of said tubular extension, an exit portfor said fluid in said extension, a valve adapted to regulate said exitport, andmeans formin part of a brake applying device forcontroll ingthe opening of said valve, substantially as set forth.

3. Brake relay mechanism asclaimcd in claimfl, in which the tubularprojection discharges freely into a. compartment from which thecirculatory fluid is withdrawn by the pump, substantially as set forth.

l. Brake relay mcchanisin as claimed in claim 2, in which the tubularprojection extends slidably through the end of the cylinder andcommunicates with the interior of the latter'through a port adjacentits, junction with the piston, substantially asset forth. j

i 5. Brake relaymcchanism as claimed in claim 2, 'in which the valve isslidably mounted in the tubular projection and seats around thecdge ofthe latter, sulistautially I as set forth. a j

-with its axis vertical and isniountcd in a ion compartment containing areserve of circulatory fluid and also adapted to enclose tlic controlvalve audits associated actuating mechanism, substantiallyas sct forth.

In testimony whereof I have signed my name to this specification.

FRANK GORDON PARN'ELLF

